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The Tatun geothermal system, located in northern Taiwan, is hosted by the Plio-Pleistocene Tatun volcanic group, consisting dominantly of andesitic lavas, domes and pyroclastic flows. During the late 1960s and early 1970s, geologic mapping, geochemical sampling, geophysical surveys, and the drilling of numerous exploration and temperature gradient wells were conducted at Tatun under the leadership of the Mineral Research and Service Organization (MRSO), the predecessor to the geothermal group at the Industrial Technology Research Institute (ITRI). Deep (1–2 km) wells encountered commercial temperatures (200–300 °C) in the Matsao area, but these initial exploration efforts were discouraged by the presence of very acidic (pH 2 as well as HCl. More reduced gases are encountered on the flanks of the system, suggesting that water-rock interaction may have at least partly neutralized the volcanic-derived fluids on the margins of this geothermal system. Scientists from Lawrence Berkeley National Laboratory (LBNL) and ITRI have been working together to develop an updated evaluation of the Tatun geothermal system, with the goal of evaluating the geothermal resource potential of the NE margins of the Tatun geothermal system (Zone C), just outside of Yangmingshan National Park. This study provides a review and analysis of existing and new fluid geochemistry data, describes new magnetotelluric data and associated 3-D modeling conducted at LBNL, and incorporates these data and analyses with information from previous studies to create an updated conceptual model for the Tatun geothermal system, with a focus on the Zone C region. These data all suggest that the Zone C area is located on the margin of the main Tatun geothermal system. An exploration well drilled by ITRI will provide important constraints regarding the thermal regime and fluid compositions for this marginal portion of the system.

The scaling of geothermal wells arising from formation of calcium carbonate is one of the major problems associated with the utilization of geothermal energy. A novel eco-friendly biological-based approach for geothermal well descaling was proposed. Thermophilic bacterial strains were isolated from geothermal areas in Taiwan and were evaluated for their calcium adsorption efficiency under the extreme conditions. Among the eight strains isolated, Tepidimonas fonticaldi AT-A2 isolated from Antun Hot Spring, Hualien showed the highest calcium adsorption capacity. The calcium adsorbing activity of T. fonticaldi AT-A2 was mainly associated with the extracellular proteins and the maximum calcium adsorption capacity (1.94 g Ca/g protein) was obtained at pH 10, 150 °C and 1 atm pressure. This calcium adsorption efficiency is much higher than that of metallothioneins and other bacterial extracellular proteins. The excellent calcium adsorption efficiency of the AT-A2 proteins indicates the potential for their applications in biological geothermal well descaling.

The Chingshui geothermal power plant was decommissioned in 1993 due to a continued decline in production. Although some geothermal exploration and field investigation had been exercised, the production potential of the reservoir is still not well understood. In this paper, numerical modeling approaches for characterization of the geothermal reservoir, investigation of reservoir production performance, and evaluation of exploitation scheme design are presented. At first, a site-scale refined grid numerical model was developed for simulating the natural state of Chingshui geothermal reservoir. Through the model, the production potential of the geothermal reservoir was estimated and the availability of water resources was assessed. We further built production model to simulate the production history during 1981–1993. From the production model, we can conclude that the abnormal drop of the reservoir production capacity is mainly caused by carbonate scaling. Potential production schemes with different reinjection designs were evaluated through the model. Simulation results indicated that a sustainable hot water production capacity of Chingshui geothermal reservoir is about 200 t/h without reinjection, and 300 t/h or even higher with reinjection which is enough for a 3 MWe power plant. The simulation results indicate that reinjection provides an effective approach for maintaining reservoir pressure during hot water/steam production.

This study analyzed patent data to explore the technological developments based on the organic Rankine cycle (ORC), which is one of the most economical and efficient methods for converting low-grade thermal energy into electricity. The patent data were obtained from the Thomson Innovation commercial database, which contains patent information from various countries and offices. After querying, filtering, and organizing the results into patent families in accordance with International Patent Documentation Center guidelines, this study analyzed data on 304 ORC-related patents. The results show that the number of patent applications increased gradually before 2006, and then rapidly from 2009 to 2011, primarily because of contributions from patent applications in China (CN) and the Republic of Korea (KR). The present findings indicate that 2009 is an important year regarding developments in ORC systems and the number of patent applications. Furthermore, the assignees from the United States (US) were the most prominent contributors. However, the most patent applications were filed in CN, indicating that the market for ORC systems in CN might offer the most potential for future development. This study also examined the top ten patent assignees, as well as the trends of the number of patent applications, size of patent families, and frequency of patent citations. The results show that all of the top ten assignees were from the US, CN, and KR. Moreover, most of them filed their patent applications in recent years, particularly after 2008. The results further indicate that the most active assignee is currently General Electric Company (US). In addition, the top five patent families and the five most frequently cited patents are briefly reviewed and discussed. The patent data analysis results indicate that the technology life cycle status of the ORC is currently in the growth stage.

The influences of various evaporators on the system responses of a 50 kW ORC system using R-245fa are investigated in this study. First the effect of the supplied hot water flowrate into the evaporator is examined and the exit superheat on the system performance between plate and shell-and-tube evaporator is also reported. Test results show that the effect of hot water flowrate on the evaporator imposes a negligible effect on the transient response of the ORC system. These results prevail even for a 3.5-fold increase of the hot water flowrate and the system shows barely any change subject to this drastic hot water flowrate change. The effect of exit superheat on the ORC system depends on the type of the evaporator. For the plate evaporator, an exit superheat less than 10 °C may cause ORC system instability due to considerable liquid entrainment. To maintain a stable operation, the corresponding Jakob number of the plate heat evaporator must be above 0.07. On the other hand, by employing a shell and tube heat evaporator connected to the ORC system, no unstable oscillation of the ORC system is observed for exit superheats ranging from 0 to 17 °C.

During 1992–2007, excessive pumping of groundwater caused large-scale aquifer-system compaction and land subsidence in the Choshui River Alluvial Fan, especially in the area of Yunlin county. The subsidence impedes surface-water runoff and endangers the operation of Taiwan High Speed Rail. Leveling, Global Positioning System (GPS), multi-level compaction monitoring well, and Differential Interferometric Synthetic Aperture Radar (DInSAR) are used to study the extent of subsidence in Yunlin and its mechanism. These sensors complement each other in spatial and temporal resolutions. A leveling network totaling 434 km in length was deployed to derive subsidence at every 1.5 km along the routes, and the result is accurate to few mm and shows a basin-like subsidence pattern centering at Tuku Township. Four multi-level compaction monitoring wells, co-located with GPS pillars, detect compactions at different depths, showing that the aquifer-system compaction (the cause of subsidence) occurs mostly below depths >200 m, where reduction of groundwater pumping is most needed. The vertical displacements from GPS and leveling agree to within 1 cm, and are larger than the cumulative compaction detected by the compaction-monitoring wells, suggesting that compaction also occurs below 300 m (the depth of the wells). The vertical displacements derived using DInSAR and 8 ENVISAT SAR images agree with the leveling result to 1–2 cm.

Taiwan High Speed Rail (THSR), which began operations in January 2007, passes through an area in Yunlin County where the largest cumulative subsidence measured during 1992–2006 exceeds 100 cm. Leveling benchmarks, GPS pillars and multi-level monitoring wells were deployed in this area to collect detailed subsidence data from October 2003 to 2006. Leveling is carried out on both ground benchmarks and survey bolts attached to THSR columns. Minimum constraint solutions of leveling networks produce estimated heights accurate to a few mm. Special attention is paid to code smoothing, ionospheric, tropospheric and ocean tidal loading (OTL) effects, so that height estimates from GPS are optimal. Leveling and GPS-derived height changes are consistent to 1 cm, and show that from Stations 210 to 240K of TSHR, the subsidence is bowl shaped. Measurements of sediment compaction in specific depth intervals at three monitoring wells indicate that most of the subsidence is caused by sediment compaction at depths from 50 to 300 m. The major compaction occurs in the interval 220–300 m and is attributed to ground water withdrawal. Large angular deflections as determined from subsidence measurements are detected at some columns, but are below the upper bound (1/1,000) of tolerance specified in the safety code. With the current subsidence and sediment compaction, no significantly reduced loading capacity of the columns is expected to occur. For a safe THSR operation, subsidence and sediment-compaction monitoring should be continued, and current ground water withdrawal in Yunlin must be reduced or stopped.

This paper estimates the coefficients of volume compressibility from variation in compressible layer thickness and changes in piezometric heads by using detail ground surface surveys and a multilayer monitoring well at a selected site (Shigang) within the Choshui River alluvial fan in west Taiwan. The paper integrates various types of in situ monitoring tools, including leveling surveys, continuous global position system (GPS) stations, multilevel layer compression and groundwater pressure headmonitoring wells, to investigate the situation and progress of the subsidence problem in the region. The results from the crossanalyses of the measured data show that surface settlement caused by the compression of strata is between the depths of 60 and 210 m where the clayey stratum within 120–180 m was most pronounced and contributes up to 53% of the total compression. The results indicate that the clayey stratum is under normal consolidation. The results also reflect the fact that 20% of settlement contribution comes from the sandy stratum within 90–120 m; the elasto-plastic behavior of this sandy stratum is clear. The coefficients of volume compressibility of the clayey and sandy stratum analysed from the stratum’s compression records; they were 6.3810 8 and 5.7110 9 m 2 /N, respectively. Ultimately, this parameter estimation would permit to control and predict land subsidence based on change in pressure head which are related to groundwater extraction. D 2004 Elsevier B.V. All rights reserved.

Land subsidence in Taiwan has increased rapidly over the past four decades, owing to heavy withdrawal of groundwater. Leveling surveys, layer compressions and groundwater level in individual layers were continuously monitored in the Choshui alluvial fan, western Taiwan. It was found that ground subsidence and layer compression were consistent with the variation of groundwater level. From multi-level compression monitoring, the layers with major compression deformation were identified. Clayey and sandy layers exhibited significant compression deformation. Conceptual models of compression behavior for clays and sands were studied based on the field data. The compression behavior of clays agreed with the Terzaghi consolidation theory. Notable, irrecoverable volumetric strains were also observed in sandy layers. They exhibited obvious elasto-plastic mechanical behavior. The high compressibility of the sand layer in the alluvial fan was attributed to the flaky sand grains in this geological region.

An organic Rankine cycle system comprised of a preheater, evaporator, condenser, turbine, generator, and pump was used to study its off-design performance and the operational control strategy. R245fa was used as the working fluid. Under the design conditions, the net power output is 243 kW and the system thermal efficiency is 9.5%. For an off-design heat source flow rate (mW), the operating pressure was controlled to meet the condition that the R245fa reached the liquid and vapor saturation states at the outlet of the preheater and the evaporator, respectively. The analytical results demonstrated that the operating pressure increased with increasing mW, a higher mW yielded better heat transfer performance of the preheater and required a smaller evaporator heat capacity, and the net power output and system thermal efficiency increased with increasing mW. For the range of mW studied here, the net power output increased by 64.0% while the total heat transfer rate increased by only 9.2%. In summary, off-design operation of the system was examined for a heat source flow rate which varied by –39.0% to +78.0% from the designed rate, resulting in –29.2% to +16.0% and –25.3% to +12.6% variations in the net power output and system thermal efficiency, respectively.

The variations of the evaporator on the system responses of a 50 kWe ORC system using R-245fa are investigated. The effect of exit superheat on the ORC system depends of the types of the evaporator. For the plate evaporator, an exit superheat less than 10 °C may cause ORC system unstable due to liquid entrainment. For maintaining stable operation, the corresponding Jakob number of the plate heat evaporator must be above 0.07. On the other hand, no unstable oscillation of the ORC system is observed for an exit superheat of 0∼17 °C when the shell-and-tube heat exchanger is used as the evaporator.